Means and method of treating wells



y 1964 J. KARPOVICH MEANS AND METHOD OF TREATING WELLS Filed Aug. 30,1960 H e age/7f reservoir 7'0 draw 0 war/as Tre a/l'ng f/u/c/ INVEN TOR.J0/7n Karpow'ch BY AGENT United States Patent MEANS AND METHOD OFTREATING WELLS John Karpovich, Midland, Mich., assignor to The DowChemical Company, Midland, Mich., a corporation of Delaware Filed Aug.30, 1960, Ser. No. 52,824

, 4 Claims. (Cl. 166-42) A This invention relates to earth welltreatments and particularly to so called formation fracturingtreatments.

It is known to use implodable frangible vessels or capsules in :wellstimulation treatments of the so-called Rock Shock type. In suchtreatments the vessel or capsule is disposed in a liquid column in awell bore adjacent to the formation to be stimulated and the hydraulicpressure is increased to the point where the capsule implodes. Theforces resulting from the implosion often 'form fractures which were notpractical to produce otherwise because of casing limitations as to thepressure it can withstand or because of limitations of surface pumpingequipment. a

While the implosion produces a violent reaction in the well bore, asecond reaction to supplement the implosion is desirable tomoreeffectively drive treating fluid into the adjacent earth formation.

- Accordingly, a principal object of this invention is-to provide animproved method of treatment of an earth well.

Another object of this invention is to provide an improved wellstimulation apparatus. V

A further object of this invention is to provide an improved method offracturing earth formations which are adjacent to the bore of an earthwell.

In', accordance with this invention an implosion capsule having disposedtherein materials which, when exposed to the well bore liquid or toshock, explodes. Thus, when the capsule "is imploded, the violentreaction attendant to "the implosion issupplemented by the explosion atthe same point along the well bore, resulting in a more effectivetreatment of the adjacent earth formation. The

invention, as well as additional objects and advantages thereof, willbest be understood when the following dean alternative form of implosiondevice which may be used in accordance with this invention.

Referring to FIG. 1, there is shown an earth well 8 having a bore wall'10 which extends from the surface 12 of the earth through earthformations 14, 16, 18, for example. Casing 20, capped by a suitablecasing head 22, extends through the earth formations 14, 16 and into theformation 18 near the bottom 24- of the well. The casing 20 is bonded tothe wall by cement 26.

A frangible capsule, indicated generally by the numeral 28, is shownsuspended from a cable 30 below the casing 20 in the well 8. The cable30 passes through the casing head 22, over a sheave 32 and to a drawworks (not shown). The capsule is held in a weighted carrier (not shown)as is conventionally done where implosion capsules are used in a welltreatment. Such weighted carriers are listed in the publication DowellTechnical Report on Rockshock, published in March 1960 by Dowell Div.,The Dow Chemical Company, Tulsa, Oklahoma. Also, the March 1960 issue ofWorld Oil magazine, in an article entitled Implosion Technique ImprovesFracturing Performance, by Donald D. Setser, notes that capsules may besuspended from the tubing in the well.

The capsule 28 comprises a frangible body part 34 capsule. In the eventthe capsule 28 is to be imploded in a non-aqueous medium, a sealedcontainer of an agent capable of oxidizing the alkali metal such aswater or hydrogen peroxide is also disposed within the capsule 28.

At the surface, a source 44 of treating fluid, a source 46' of treatingfluid with propping agent, and a gas reservoir 48 are coupled to thewell through the lines 50, 52, 54, valves 56, 58, 60, 62 and pumps 64,66. Treating fluids and treating fluids with propping agent and theiruses are disclosed in Farris Reissue Patent No. 23,733, issued Nov. 10,'1953. I

A vent valve 76 and pressure gauge 78 are coupled to the casing head 22.v

in operation, with the casing head 22 opened, the

capsule 28 is lowered into the well 8 on the cable 30 to' pling meansfor holding the capsule 28 belowv the'icab le 30 have been shown onlyschematically.

The well bore may be, if desired, at least par-tiall filled with liquidas the capsule 28 is lowered into position. 1 r

When the capsule is in position, the casing head is closed and, withvalves 56, 62 closed, treating fluid from the reservoir 44 is pumped bymeans of pu-mp'64 into the well 8. The vent valve 76 is opened until thewell bore is filled with treating fluid and is then closed while thepumping of treating fluid is continued. In some cases sufficienthydrostatic head on the capsule to collapse it may be reached withoutfilling the well completely.

Afterthe vent valve is closed, it is sometimes desirable to open valve56 and, by means of pump 66, inject gas from the reservoir 48 intotheliquid being pumped into the'well, in accordance with the teaching ofUS. Patent No. 3,004,594 toF. W. Crawford, especially lines 17 through28 of column 2., for example.

The hydraulic pressure in the well bore is increased to cause theimplosion of the capsule28, causing a violent reaction in the well bore,especially adjacent to the point along the bore where the implosionoccurs. This violent reaction is in itself often sufiicient to initiatefractures in the adjacent earth formations. However, in the instantinvention the implosion of the capsule in turn results in an explosionin the well bore adjacent to the formation being treated. This explosionsupplements the violent reaction of the implosion and causes moreextensive frac turing of the formation than occurs when an implosionalone is used in the treatment.

Examples of materials which may be disposed within the vessel 28 tocause an explosion when the vessel implodes are metal hydrides,metallo-organic compounds, alkali metal, e.g. sodium in a form whichpresents a large surface area per unit weight, and shock sensitiveexplosives.

Metal hydrides which may be used include aluminum hydride.Metallo-organic compounds which may be used include metal alkyls such astrimethyl aluminum, triethyl aluminum, triethyl magnesium, and Grignardtype compounds.

The addition of a capsule which may readily be ruptured and which may bemade of polytrifluorochloroethane, for example, containing hydrogenperoxide will cause the explosive reaction to occur on implosion. of thevessel 28 even when water is not present in the well bore adjacent tothe capsule. 28. The capsule 37 of hydrogen peroxide, of course,ruptures when the capsule 28 is irnploded.

When shock sensitive explosives are provided in the capsule 28, however,there is no need to provide peroxide or water as the force resultingfrom the implosion detonates the explosive regardless of the nature ofthe surrounding liquid medium in which the capsule 28 is disposed. V

7 FIG. 2 shows a sealed vessel or capsule 80 which is similar to thevessel or capsule 28 except that it has a pair of electrical leads 8 2,84 extending from the exterior to the interior thereof, the leads havingan electrically energizable filament 86 connected across them.

The capsule ,80 has readily oxidizable material such as magnesium,aluminum or zirconium foil, wool, or ribbon 88 disposed therein inphysical contact with the filament a 86; An oxygen atmosphere exists inthe capsule 80'. The capsule 80 is suspended in any suitable manner froma cable 90 which has electrical conductors connected to the leads 82, 84and, as 'further shown schematically by the leads 92, 94 and switch 96,to a battery 98 or other sourcefor energizing the filament 86. Thebattery may be disposed at the surface 12 of the earth, for example.

In operation the filament 86 is energized by closing the battery circuitwhile the capsule is in place in the well bore adjacent to the earthformation to be treated and the liquid medium in the bore is under anappropriate pressure. Energizing the filament, causes the foil, wool orribbon 88 to fire,-causing thermal stresses which, with the pressure ofthe liquid medium in the well bore, cause the capsule to collapsesuddenly. The explosion of the material 36 then is initiated asdescribed in connection with the capsule 28 in FIG. 1.

-"Following the implosion and explosion, it is usually desirable toclose the valve 60 and open valve 62 in the line 52 leading to thereservoir 46 of treating fluid with propping agent. Thus, propping agentis pumped down the well bore and into the newly created or extendedfractures 100' (see FIG. 1).

From the above description it is apparent that the instant inventionprovides a novel, safe means and method of fracturing or otherwisestimulating an earth well. For

example, this invention is also applicable to acidizing and othertreatments where the formation must be broken 4 What is claimed isi 1. Amethod of treating an earth well which comprises: V

(a) loading into a hollow frangible walled vessel explodable materialfrom the class consisting of metal hydrides, metallo-organic compounds,alkali metals,

' and shock sensitive explosives,

(b) sealing said vessel,

(c) lowering said sealed vessel position in said earth well,

(d) covering said sealed vessel with liquid,

(e) subjecting said vessel to sufiicient hydraulic pressure to compressfluid in said well bore and to implode and shatter said vessel, and

(f) on shattering said vessel, exposing said explodable material toambient Well bore conditions which inito a predetermined tiatedetonation of said explodable material, .thereby' vessel, when sealed,has an internal pressure which. is

a minor fraction of the pressure at which it iinplodes.

4. A method in accordance with claim 1, wherein treatingagent is pumpedinto said earth formation. following said detonation.

References Citedin the file of this patent UNITED STATES PATENTS Re.23,733

Farris Nov. 10, 1953 2,361,558 Mason Oct. 31, 1944 2,756,826 Ebaugh July31, 1956 7 2,785,633 Ewing et al Mar. [19, 1957 2,887,954 Swed May 26,1959 2,911,046 Yahn Nov. 3, '1959 2,932,251 Hamilton Apr. 12, 1960Chestnut Oct. 3, 1961

1. A METHOD OF TREATING AN EARTH WELL WHICH COMPRISES: (A) LOADING INTOA HOLLOW FRANGIBLE WALLED VESSEL EXPLODABLE MATERIAL FROM THE CLASSCONSISTING OF METAL HYDRIDES, METALLO-ORGANIC COMPOUNDS, ALKALI METALS,AND SHOCK SENSITIVE EXPLOSIVES, (B) SEALING SAID VESSEL, (C) LOWERINGSAID SEALED VESSEL TO A PREDETERMINED POSITION IN SAID EARTH WELL, (D)COVERING SAID SEALED VESSEL WITH LIQUID, (E) SUBJECTING SAID VESSEL TOSUFFICIENT HYDRAULIC PRESSURE TO COMPRESS FLUID IN SAID WELL BORE AND TOIMPLODE AND SHATTER SAID VESSEL, AND (F) ON SHATTERING SAID VESSEL,EXPOSING SAID EXPLODABLE MATERIAL TO AMBIENT WELL BORE CONDITIONS WHICHINITIATE DETONATION OF SAID EXPLODABLE MATERIAL, THEREBY INDUCING THEFORMATION OF FRACTURES IN THE WALL OF SAID EARTH WELL ADJACENT BY MEANSOF THE SHOCK WAVE OF SAID IMPLOSION AND THE DETONATION OF SAIDEXPLODABLE MATERIAL.